Environmental concern raises a demand for removal of carbon dioxide (CO2) from, e.g., combustion gases, and subsequent processing or storage of the CO2, to reduce emission to the atmosphere thereof. In known technologies for ammonia or ammonium based CO2 capture, CO2 is converted to ammonium carbonate or ammonium bicarbonate in dissolved or solid form. It is known to regenerate the ammonia or ammonium compounds used for CO2 capture by release of CO2 under controlled conditions.
Resnik, K. P. et al. (2004) Aqua ammonia process for simultaneous removal of CO2, SO2 and NOx, Int. J. Environmental Technology and Management, Vol. 4, Nos. 1/2, pp. 89-104, discloses that the aqueous ammonia process can remove CO2 and other contaminants that may exist in flue gas. Test results pertaining to the ammonia/carbon dioxide reaction in a semi-continuous reactor system are presented. Regeneration test results, including solution-cycling between the regeneration and absorption steps, are also presented.
WO 2006/022885 discloses cleaning of combustion gas to near zero concentration of residual contaminants followed by the capture of CO2. The CO2 is captured from cooled and clean flue gas in a CO2 absorber utilizing an ammoniated solution or slurry in the NH3—CO2—H2O system. Regeneration is accomplished by elevating the pressure and temperature of the CO2-rich solution from the absorber.
It is, however, an ever existing desire to further improve CO2 capture technologies in respect of, e.g., ammonia loss, power consumption, or chemical reaction rate.